Cavity-Quantum Electrodynamics with Quantum Dots – University of Copenhagen

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Cavity-Quantum Electrodynamics with Quantum Dots

Enhancing the interaction between a single photon and a single quantum emitter is an essential requirement needed for many quantum information schemes. To this end solid-state quantum dots embedded in photonic nanocavities have proven to be very promising. Quantum dots are excellent solid-state single-photon sources, however decoherence from the environment due to phonons requires special attention. The physics of phonon dephasing is rich and challenging and cavity QED provides a way of gaining additional insight into these processes.

Top: Example of a photonic crystal nanocavity fabricated in GaAs, which is obtained by leaving out three holes from a 2D photonic crystal membrane. Bottom: Illustration of a quantum dot in the cavity emitting light vertically out of the structure.

In this project we study the fundamental quantum optical properties of single quantum dots embedded in state-of-the-art photonic nanocavities. Depending on the coupling strength between the lowest energy transition in the quantum dot and the single cavity mode, we can investigate both the weak and strong coupling regimes of cavity quantum electrodynamics (CQED). We have recently observed for the first time that the dynamics of spontaneous emission in a photonic nanocavity reveals inherent non-Markovian photon-quantum dot interaction due to the strong light-matter coupling strength [1]. The inherent many-body nature of the quantum dot system results in the observation of phenomena unique for solid-state systems, such as non-Markovian (memory dependent) interactions between the quantum dot and lattice vibrations (phonons). We investigate these effects by performing time-resolved measurements on the emission from a quantum dot, while tuning the frequency of the cavity mode. We also perform photon correlation and indistinguishability measurements in order to investigate the coherence of the emitted photons, which provide valuable information about the quantum dot – phonon interactions.